Sal Suds or Castile Soap – Which One Should You Use?

I talk a lot about the exceeding versatility of Dr. Bronner’s Castile Soap and Dr. Bronner’s Sal Suds.  There are so many overlapping uses.  But is there any time in which they aren’t interchangeable?  Yes, but just a few.

Castile soap is primarily designed for the body.  The blend of oils (coconut, olive, palm, jojoba, and hemp) are designed to be the most nourishing to our skin.  But wait, there’s more.  Because it is such a beautifully simple soap, it also cleans many other things amazingly well, whether it’s your dog, your sinks, or your floors. You can find details of all these uses on this Castile Soap Dilutions Cheat Sheet.

Because Castile soap is a true soap, it reacts with the minerals contained in hard water. (Here’s my test to find out if you have hard water.)  The more dissolved minerals there are, the “harder” the water.  The reaction of soap with these minerals in the water leaves behind an insoluble film that’s commonly called “soap scum”.  This term is a bit of a misnomer, because it’s not actually soap that remains, but a precipitate of minerals.

You’ll only notice this on shiny objects that are left to air dry.  They will take on a whitish film. (Read my post on eliminating soap scum.) Also, absorbent fabrics like towels and cloth diapers will become stiff and lose their absorbency. (But laundry in hard water is still doable – Read more here.)

Enter Sal Suds.  This is our biodegradable household cleaner developed by my dad. Sal Suds doesn’t react with hard water.  It rinses cleanly and leave surfaces sparkling.  No more film on the tub or towels!  For it’s multitude of uses, see the Sal Suds Dilution Cheat Sheet.

That’s all well and good, but I haven’t answered that initial question of what to use when.

Situations where I exclusively use Castile:

  • Myself – Head to toe.
  • My animals – Any Castile soap scent on my dog. Baby Unscented on my cat.
  • Pest Control – Only Castile soap has this ability to eliminate insects.

Situations where I exclusively use Sal Suds:

  • Dishes
  • Cars
  • Most Laundry – sometimes, as with bedding, I use Castile soap.

Other than these few cases, I reach for whichever is closer at hand.

Now you know what to use, but perhaps you want to know why?

Soap and detergent are both surfactants.  The word “surfactant” is a portmanteau of “Surface Active Agent.”  If you’ve ever done a belly flop into a pool, then you’ve felt the power of surface tension. Surfactants break through the surface tension of water and make water really soak in.

My brother Mike says that:

Surfactants make water wetter.

The second magical power of surfactants is that they make oil and water coexist.  Which they don’t otherwise like to do.  This is why you can’t just rinse oil off your hands.  The water runs over the oil like it’s just not there.  And it just doesn’t care.

Now brace yourselves – you’re about to learn some Greek!

Surfactants solve the oil/water repulsion because one end of each surfactant molecule is hydrophilic and the other end is hydrophobic.

Hydrophilic literally means “water (hydro) loving (philic).”  This end of the surfactant molecule grabs hold of water.  On the other side, hydrophobic means “water (hydro) fearing (phobic).”  A little exaggerated perhaps, but this end grabs the oil.

But we’re not talking about just one.  Surfactant molecules work in groups.  In a solution, they float around looking for oil molecules and snag with those hydrophobic tails, totally surrounding each oil molecule so there’s no part of the oil molecule left exposed to water.  This little nugget is called a micelle.

The outside of this micelle is now entirely hydrophilic, which means instant attraction to the passing rinse water which carries it all away.

It’s like they’re filling those oil molecules with a whole lotta love and reaching out and connecting them with their former enemy, those water molecules.  And once they’re connected, they realize it’s not so bad.  They can get along. They can hang out together.  I think there’s a larger lesson here.

You still with me?

So they’re both surfactants.  Now for some differences.

Soap is close to nature, made by a beautifully efficient one-step reaction of combining oil (coconut, palm, olive, jojoba, and hemp for our Castile) with a strong alkali such as sodium or potassium hydroxide (the first also known as lye).  Out of this combo, you get soap, glycerin and water. Bam!  No leftovers. No waste. Beautiful.

Detergents are more complex and must be synthesized.  They were developed during the World Wars when the oils needed for soap were scarce.  They can start with botanical substances (such as coconut oil for our Sal Suds) or with petroleum derivatives. And the uses of detergents is vast and wide.

Tidy as it would be, I can’t sum it all up by saying, “Soap good. Detergent bad.”  That would be a gross oversimplification.  There are bad soaps (not ours, of course) that are poorly made with bits of unreacted alkali floating around in them ready to saponify your very body.  You become walking bar of soap.  Ouch!

And there are excellent detergents, such as our Sal Suds, which is super duper tough on grease and completely clean rinsing, yet mild and biodegradable.

So that’s a little bit more about the magic of cleaning and the beauty of chemistry.

117 thoughts on “Sal Suds or Castile Soap – Which One Should You Use?

  1. Does Sal Suds have a germ-killing, antibacterial properties in it? In other words, do the EO’s have those properties? Thanks.

    • Hi Andrea- The term “antibacterial” means that the product must kill 99.9% of germs. The term “disinfectant” means that the product must kill 99% of germs. Dr. Bronner’s soap (Castile soap and Sal Suds) is part of the “disinfectant” category. Soap works by removing. It latches on to dirt, grime, germs, etc. and takes them away. It’s the soap that’s doing the heavy lifting here, not the essential oils. The only thing that kills bacteria is a pesticide, and soap is not a pesticide. That means the short answer is, no, soap will not kill bacteria or anything else. Soap eliminates it, though. This is a question I get a lot – and it’s a good one – so I wrote about it in-depth recently:

  2. We will be putting in Dekton countertops in our home and I was wondering if the Castile or Sal Suds work on this surface.

    • Hi Lisa- Either Sal Suds or Castile soap will clean your beautiful new countertops… well, beautifully!

  3. I was surprised to see sodium lauryl sulfate in the ingredient list for Sal Suds. I’ve seen it on the list of questionable ingredients for personal care products. It makes me very hesitant to buy Sal Suds. Can you explain why it is an ingredient in an all natural product?

    • Hi Lori- It’s great to hear you’re a fellow label reader! First, Sal Suds not a true soap like our Castile soaps. It is a biodegradable, all-purpose household detergent – meaning it is synthetic. But not everything synthetic is bad, in the way that not everything natural is good. Sal Suds is formulated with SLS because of its keen ability to cut through grease and grime and to generate suds. SLS can be a skin irritant for some people because it can be so drying. It is so good at picking up oils that it pulls them right out of our skin. You won’t find SLS in any of our personal care products, and personal care products (shampoos, soaps, toothpaste and such) that include it should be avoided. Studies have consistently shown that SLS is safe to use in low concentrations and in products that are meant to be rinsed off – both of which are true of Sal Suds. Of course our all-natural Castile soap does an excellent job of household cleaning as well. For a deeper dive into SLS, refer to my blog post here:

    • Thank you for your response! I did read on some of the older questions/answers and you addressed the SLS questions very well! I have absolutely no hesitation now to purchase Sal Suds! I’m glad your company is so concientious about product quality and being earth friendly!

  4. I live on Vancouver Island in Canada and would like to purchase Dr. Bonner’s Sal Suds. Can you tell me where I can buy it? I’m in Sidney/Victoria area.

    • Hi Susan- Our products are usually found in the body care section of most natural grocers, supermarkets and pharmacies. A distributor in your area also can tell you what stores in your area carry our products. Here’s a list of distributors:

  5. Can Sal Suds be used in hand soap? I know you explained in previous comments that head to toe you use Castile Soap but when washing dishes by hand with the Sal Suds in an essential oil dish detergent recipe it is touching our hands of course.

    • Hi Christina- It is safe, but more drying to hands than our Castile soap. Although no more so than a conventional soap.

  6. it is advised to use a liquid soap when mixing Neem oil concentrate with water. Should I use Sal Suds or Castile Soap for this?

    • Hi Arun- It depends on what you will be using the soap and Neem oil for. If it is for use on the skin or body, use the Castile soap. Sal Suds is our all-purpose household cleaner.

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